Pumps for pumping viscous fluids from relatively large containers such as cylindrical drums conventionally employ a follower plate, with the pump mounted above an orifice through the follower plate. U.S. Pat. No. 4,792,063 to Moore, which is hereby incorporated by reference, describes such pumps. In such systems, the follower plate is introduced into the container as the liquid is evacuated via pneumatic, hydraulic, or spring-driven means or simply by the vacuum that results from the removal of material. The pumping action creates a partial vacuum as the follower plate is drawn into the container, until the pump loses the ability to withdraw further material from the drum. The descending follower plate scrapes excess material from the sides of the container and forces the liquid into the pump to prime it and keep it primed. Normally considerable excess material is left in the container at the point that no further material can be removed. A bag often is inserted into such containers prior to filling to facilitate removal of this excess material, but this does not provide an efficient way to remove that material.
U.S. Pat. No. 5,887,752 discloses an apparatus for extracting material from containers. The apparatus includes a pump, a follower plate and a pump section tube inserted in the follower plate and connected to the pump. The follower plate is inserted in the container and lowers as material is extracted. When the follower plate reaches a point where the pump no longer has the ability to pump material, there remains material in the container. A bladder is then inflated via an air source and material is forced towards the follower plate where it can be extracted. However, as the bladder is inflated it may be ingested into or block the pump section tube.
The present invention is aimed at overcoming one or more of the problems identified above.